To protect video/audio content from unauthorized consumption, encryption techniques are usually used to scramble video/audio content during delivery or during recording. The Digital Video Broadcasting (DVB) standard has specified a common scrambling algorithm (CSA) to scramble video/audio transport stream packets encoded in the form of MPEG-2. The DVB common scrambling algorithm is a proprietary algorithm and details of the algorithm have not been published. However, it has long been stipulated in the communications industry that the DVB common scrambling algorithm is weak and should be replaced by a stronger encryption algorithm based on modern cryptographic techniques.
The US Society of Cable Telecommunications Engineers (SCTE) has standardized a method, referred to as SCTE-52, for scrambling MPEG-2 transport stream packets using the Data Encryption Standard (DES) under Cipher Block Chaining (CBC) mode. However, the SCTE scrambling standard does not specify how to generate the initialization vector (IV), a parameter which will be used by the DES encryption under cipher block chaining mode. Moreover, the DES encryption algorithm is no longer a strong algorithm due to a number of rigorous cryptanalysis during the last two decades. For this reason, the common scrambling standard developed by the Advance Television Systems Committee (ATSC) replaces DES with the cryptographically stronger triple-DES (TDES) with 168-bit key. The ATSC common scrambling standard also mandates that the initialization vector for the triple-DES under cipher block chaining mode be all zero. Nevertheless, both the DES algorithm and triple-DES algorithm are inferior to the Advanced Encryption Standard (AES) with respect to both security strength and implementation efficiency. In view of the above, it would be beneficial if methods and apparatus were developed which utilized AES for the scrambling of video/audio transport stream packets over Internet Protocol (IP) networks.